The UK could be vulnerable to a high-level online attack because of a lack of talented and skilled cyber experts.

Companies and government agencies say they are struggling to recruit people into the cyber-security profession.

A senior figure from the intelligence agency GCHQ has told Sky News he is concerned the organisation might not have the right people to deal with a sophisticated assault on the UK's online networks.

A source from GCHQ said: "Cyber space is a really complicated area... lots of people are interconnected to it so there are going to be vulnerabilities but where they are, I can't tell you."

In an effort to find new talent, the Cabinet War Rooms in central London have been hosting the Cyber Security Challenge - a 24-hour simulated cyber attack.

The scenario is based on an assault by a foreign government on the UK's financial systems.

As part of the 24-hour exercise, teams of young cyber defenders have been shown fake news reports, given briefings by the national defence community and tip-offs by undercover operatives.

Will Shackleton, a competitor, explained: "We've been given some data that has been captured from the company's network and we had to investigate it.

"We found a piece of malware inside it and we are currently trying to analyse the malware and work out what it is doing, who sent it, who it was written by and if it's doing anything, stealing anything, what it's doing within the company."

It is a competition - but all the candidates will be introduced to possible employers.

Stephanie Daman, chief executive of Cyber Security Challenge UK said: "We know they have the right sorts of skills, but none of them are currently in the cyber-security profession.

"This is what we call the hidden talent that we have in this country that we can't seem to reach out to bring into the profession."

Government figures show cyber crime is a huge problem - 93% of large businesses and 87% of smaller ones have reported a cyber breach in the past year.